Conventionally, as shown in FIG. 6, a carcass (a) of the pneumatic tire such as the tire for a passenger car is formed by rolling up a sheet of a carcass ply into the cylindrical shape. Therefore, the above mentioned carcass (a) has an overlapping portion (b) so as to connect the ply edges to each other. The overlapping portion (b) is usually set to be narrow in the tire circumferential direction, that is, the width is set to be not more than 10 mm.
However, in such a conventional tire, the difference in the rigidity of the carcass occurs at the overlapping portion (b), and dynamic balance is deteriorated. As the result, the vibration of the tire while running is generated so as to deteriorate the ride comfort. And also, the overlapping portion causes a uneven difference on the tread surface so that the exterior of the tire is deteriorated.
When the carcass is composed of two or three plies, the difference in the rigidity of the carcass can be mitigated to some degree by shifting the overlapping portions of the plies to the tire circumferential direction. But the dynamic unbalance can not be improved so that restraining the vibration of the tire and enhancing ride comfort are far from being attained.